In the serial recording apparatus (the apparatus is a recording apparatus in the sense that the apparatus records characters, graphics or the like on a recording medium, e.g., paper), a recording head has a plural number of dot-forming elements, which are linearly arrayed in the paper feeding direction. Those dot-forming elements may be impact dot wires, ink-jet nozzles, heat-generating elements, or the like. The dot-forming elements thus arrayed are selectively driven in accordance with the image data representative of patterns of characters, graphics and the like, and prints patterns of dots as the reproduction of the original patterns on a recording sheet. Sometimes, one or more of those dot-forming elements becomes defective to lose its dot forming capability.
In the print produced by the recording head including a defective dot-forming element, nothing is printed at the location printed by the defective dot-forming element, or if something is printed thereat, an optical density at the printed location is remarkably reduced. This leads to a reduction of the print quality.
When the dot-forming element or elements of the recording head are defective, it is necessary to repair the recording head or to replace the recording head with a new one. This costs a lot of time and labor. Further, the serial recording apparatus must be left inoperative during the repair and replacement of the recording head.